The present invention critically recognizes that intergranular exchange in perpendicular recording media is one of the most important parameters to know for improving performance. As understood herein, intergranular exchange affects the media signal-to-noise by controlling the size of the crosstrack correlation length and by affecting the size of the written transition. It also affects thermal stability and adjacent track erasure. Accordingly, the present invention recognizes that it is important to know whether a particular design results in too much intergranular exchange or too little intergranular exchange.
Despite its important role in performance, the present invention further recognizes that an established method for measuring intergranular exchange has not been provided. As understood herein, the value of intergranular exchange can be used to guide designers in the direction the media should be developed, i.e., more exchange or less exchange. The value of intergranular exchange can be used to change coercivity, and it can also be used to change the slope of the hysteresis loop. Thus, as recognized herein knowing the value of intergranular exchange is useful because exchange is a key player in media performance issues such as what signal-to-noise ratio (SNR) can be expected, how thermally stable a media is, and how susceptible a data track is to erasure from writing adjacent tracks. Furthermore, the present invention recognizes that once these parametrics (SNR, thermal stability, etc.) of various disks are associated with a value for intergranular exchange, information relating to improving disk design to achieve optimal intergranular exchange can be provided.